The invention disclosed herein relates to apparatus for applying heat-shrinkable sleeves of plastic film to containers. The containers may be bottles in which case the sleeves are deposited over the neck and cap of the bottle and then shrunk with heat to serve as a security device for preventing or, at least indicating, unauthorized opening of the bottle.
Apparatus of the type mentioned is known in which a flattened tube is formed in a roll so that there is a crease or fold line at each edge of the tube. After being taken off of the roll, the tube is folded onto intermediate crease lines and cut into segments or short sleeves. After being cut, the sleeves pass through a free space and become nipped by two rollers. The rollers feed the sleeve through a guide that has a converging channel which causes the sleeve to open so, as it leaves the guide, a moving bottle catches one edge so that the sleeve slides over the mouth end of the bottle which is then transported to a device that crimps the sleeve after which it is subjected to heat for shrinking it tightly onto the bottle. This arrangement is disclosed in French Laid Open specification No. 2,503,689. At the inlet end of the guide there is a pair of rollers which are spaced from the cutter by approximately the length of a sleeve or slightly less. The rollers are driven with a greater speed than the tube withdrawal device. This known apparatus is adapted for handling relatively short sleeves made of rather stiff film material. A drawback of the known apparatus is a lack of sufficient guidance of the tubular film in the zone between the cutter and the creasing device as the two rollers engage the sleeves only when the sleeves have entered into the guide in which they are caused to spread open. Experience with this known device reveals that it frequently causes buckling of the film tubes before they are cut and to tilting, retardation or actual sticking of the separated sleeves in the zone between the cutter and the creasing and sleeve opening guide. The problem is particularly acute when the sleeves are short, as the latter, after separation from the tube must traverse a short distance through free space before the sleeves are grasped by the pair of rollers at the inlet of the guide device. Short sleeves are also inclined to tilt in the zone of the guide device, caused by friction on the guide channel. The known device is, therefore, unreliable and requires frequent operator involvement.